Create Docker container setup for the project

[Ryu1845]

This pull request creates a Docker container setup for the alignment-minetest project. (solves #42)

This PR is a Work in Progress.

To do

• Working Dockerfile
• Add build instruction for the container
• Push to a docker repository (?)
• Optimize build speed (?)

[rk1a]

this got me wondering, will we need a separate Dockerfile for clients?
If this is specifically for running a server then we actually don't need to build with SDL at all.
On the other hand, I guess initially we will have server and client(s) running on the same machine, maybe even the same docker container..
So in case of a single Dockerfile it probably would make sense to not hardcode the entry point here

[Ryu1845]

CMD is just a default, we could make a cli with support for the different options as an entry point maybe?

[rk1a]

yes, that sounds good. even simpler: optionally pass a any script that is being used as entrypoint

[CLAassistant]

All committers have signed the CLA.